1. Field of the Invention
The present invention relates to a styrene-based copolymer and a process for production thereof, more particularly a copolymer of styrene and maleic anhydride excellent in impact resistance, heat resistance and transparency, being preferable as the material for various industrial goods or household electric appliances, and a process for an efficient production of said copolymer.
2. Description of the Related Arts
Copolymer of styrene and maleic anhydride (styrene-maleic anhydride copolymer) is generally a styrene-based resin which is high in heat-distortion temperature and excellent in transparency, but has a disadvantage of being so low in impact resistance that its molding is easy to break.
In order to overcome such a disadvantage, a process to improve impact resistance by adding a reinforcing agent containing rubber and the like as the main component to styrene-maleic anhydride copolymer has been proposed (Japanese Patent Publication No. 13541/1981). Though the said process may serve in improving the impact resistance to some extent, it involves a new problem that transparency is reduced.
Another process in which polycarbonate is added to styrene-maleic anhydride copolymer is disclosed (Japanese Patent Publication No. 27133/1982). According to the said process, an excellent transparency is attained, but a large amount of polycarbonate must be added to give a sufficient impact resistance, which results in lowering of the fluidity, causing poor moldability.
Moreover, a process in which rubber is dissolved into styrene monomer and maleic anhydride is added thereto to react, is disclosed (Japanese Patent Publication No. 7849/1980). According to the said process, the impact resistance is improved, but the transparency comes to be reduced.
Furthermore, a method in which diamine is reacted with styrene-maleic anhydride copolymer to form cross-linking structure has been proposed (Japanese Patent Publication No. 39651/1981). According to said process, however, the degree of cross-linking becomes so high since the amount of diamine is very large. As the result, the fluidity comes to be lowered and the insoluble content (gel) increases, which causes the moldability lowered, while impact resistance is not so improved.